Using Siri to mark reminder list items as not complete (instead of always adding new)

I have created a Grocery list in the reminder app. I can "unmark" items that are already in the list, and they become "not complete" and go to the top of the list (thereby creating my grocery shopping list for the day).

Having a comprehensive list of ALREADY EXISTING items in my grocery list (normally marked as complete) allows me to read through the entire list and make a good shopping list (marking each needed item as "not complete" as I check my pantry and fridge).

I'm trying to do the same thing with Siri (via my Apple Watch), but if I say "Add apples to my grocery list," Siri creates a completely new list item called Apples, so I end up with a duplicate item (two items in my list, both called Apples).

If I say "Mark Apples not complete," Siri will (sometimes) look for an existing item called Apples and mark it as not complete, but this cannot be done for more than one item at a time, and it doesn't work consistently. If I say "Mark cereal not complete," Siri looks for "serial" instead of "cereal." Other times, Siri just gets confused and performs a web search.

Is there a better way? I like being able to say "Add apples bananas eggs to my grocery list" (and having three separate items added), but that's no good because it creates the duplicate list entries. Is there a similar command that will cause Siri to consistently use existing items whenever they already exist in my list?